Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Tungsten carbide and fiberglass dust are allowed up to 5mg/m^3 in non-protected 8-hour work environments, day-after day. This is basically saying they are only twice as toxic as "non-classified dust". Each 1 mm hole in a 0.064" PCB is about 2 mg of material. If 10% floats away as fine dust in a smallish 20 m^3 room, then you need about 500 holes before a fan needs to be placed in a window. This matches well enough for our intuition. The amount of drill bit metal that escapes, by comparision, is next to nothing, but if you wear out 0.1% of a 10 gram bit in a routing application in a small 20 m^3 room, you've met OSHA and ACGIH's max for daily 8 hour exposure. The concern is usually with agressive sanding applications. There is also cobalt in these blades that is 5 times more dangerous, but 10x to 30x less of it.

An interesting thing is that ACGIH says hardwood dust is 5 times more dangerous. This isn't to say fiberglass isn't really unhealthy, but that you should take serious precautions to not breath hardwood dust, which goes against my intution, but I'll try to remember it.

This is not off topic because OSHA doesn't regulate DIY, so I think protecting ourselves is integral to our efforts. BTW, weller says lead fumes result from soldering, and some rosin turns into benzene (a carcinogen). The ACGIH recommendation for rosin is not a value but "as low as possible".